U.S. patent number 5,710,093 [Application Number 08/718,020] was granted by the patent office on 1998-01-20 for hydrogenation catalyst with improved attrition resistance and heat dissipation.
This patent grant is currently assigned to Intevep, S.A.. Invention is credited to Juan Jose Garcia, Enzo Peluso, Luis A. Rivas, Daisy Rojas.
United States Patent |
5,710,093 |
Rivas , et al. |
January 20, 1998 |
**Please see images for:
( Certificate of Correction ) ** |
Hydrogenation catalyst with improved attrition resistance and heat
dissipation
Abstract
A catalyst support includes substantially spherical particles of
a substantially homogeneous mixture of at least two compounds
selected from the group consisting of refractory inorganic oxides,
refractory inorganic carbides, refractory inorganic nitrides and
mixtures thereof, wherein said particles have a surface area of at
least about 30 m.sup.2 /g, an average pore diameter of at least
about 150 .ANG., and a particle size of at least about 0.1 mm. The
support may be used in a catalyst system to support a Group IVb and
a Group VIII metal in a catalyst system useful for hydrogenation of
carbon monoxide into C.sub.2 + hydrocarbons. A method is also
provided for preparing the catalyst support and system.
Inventors: |
Rivas; Luis A. (Miranda,
VE), Peluso; Enzo (Miranda, VE), Rojas;
Daisy (Caracas, VE), Garcia; Juan Jose (Caracas,
VE) |
Assignee: |
Intevep, S.A. (Caracas,
VE)
|
Family
ID: |
27003294 |
Appl.
No.: |
08/718,020 |
Filed: |
September 20, 1996 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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399239 |
Mar 6, 1995 |
5648312 |
|
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366265 |
Dec 29, 1994 |
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Current U.S.
Class: |
502/439; 502/178;
502/239; 502/242; 502/258; 502/259; 502/260 |
Current CPC
Class: |
B01J
27/224 (20130101); B01J 37/0072 (20130101); C07C
1/0435 (20130101); C10G 2/33 (20130101); B01J
35/108 (20130101); B01J 35/1014 (20130101); B01J
35/1038 (20130101); B01J 35/1061 (20130101); C07C
2521/08 (20130101); C07C 2527/224 (20130101) |
Current International
Class: |
B01J
27/224 (20060101); B01J 27/20 (20060101); B01J
35/10 (20060101); B01J 35/00 (20060101); B01J
37/00 (20060101); C07C 1/04 (20060101); C07C
1/00 (20060101); C11D 021/06 (); C11D 021/08 ();
C11D 027/224 () |
Field of
Search: |
;502/439,178,239,242,258,259,260,325,326,337,349 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Caldarola; Glenn
Assistant Examiner: Ghyka; Alexander G.
Attorney, Agent or Firm: Bachman & LaPointe, P.C.
Parent Case Text
This is a Division of application Ser. No. 08/399,239 now U.S. Pat.
No. 5,648,312 filed Mar. 6, 1995, which is a Continuation-In-Part
of application Ser. No. 08/366,265 filed Dec. 29, 1994, now
abandoned.
Claims
What is claimed is:
1. A method for preparing a catalyst support, comprising the steps
of:
forming a suspension consisting of silicon carbide and silica in a
basic aqueous solution;
adding a pore size controlling agent to the suspension;
forming droplets of the suspension;
passing the droplets through an inert organic liquid phase so as to
form the droplets into spheres;
passing the spheres through an aqueous acidic solution so as to
provide at least partially solidified spheres of said catalyst
support containing a substantially homogeneous mixture of said
silicon carbide and silica.
2. A method according to claim 1, further comprising the step of
drying said at least partially solidified spheres so as to provide
dry spherical particles of said catalyst support.
3. A method according to claim 3 further comprising the step of
calcining said dry spherical particles at a temperature of between
about 350.degree. C. to about 600.degree. C. so as to provide
calcined spherical particles.
4. A method according to claim 3, further comprising the step of
hydrothermally treating said calcined spherical particles so as to
provide said hydrothermally treated particles having an average
pore diameter of at least about 150 .ANG..
5. A method according to claim 4, further comprising the step of
calcining said hydrothermally treated particles at a temperature of
between about 350.degree. C. to about 600.degree. C.
6. A method according to claim 5, wherein said catalyst support has
a surface area of at least about 30 m.sup.2 /g and a particle size
of at least about 0.1 mm.
7. A method according to claim 1, further comprising the step of
adding a viscosity controlling agent to said suspension so as to
provide said suspension with a viscosity of at least about 50 cp at
25.degree. C.
8. A method according to claim 1, wherein the pore size controlling
agent is selected from the group consisting of
hexamethylenetetramine, urea, water soluble starch, and mixtures
thereof.
9. A method according to claim 1, wherein said suspension has a pH
of between about 9 to about 10.
10. A method according to claim 1, wherein said suspension forming
step further comprises the steps of providing a colloidal
suspension of said silica, providing said silicon carbide in the
form of particles having a particle size of less than or equal to
about 150 .mu.m, and mixing said silicon carbide with said
colloidal suspension.
11. A method according to claim 1, wherein said suspension forming
step further comprises the steps of providing a colloidal
suspension of said silica, providing said silicon carbide in the
form of particles having a particle size of less than or equal to
about 50 .mu.m, and mixing said silicon carbide with said colloidal
suspension.
12. A method according to claim 1, wherein said droplet forming
step comprises forming droplets of said suspension having a droplet
size of between about 0.1 mm to about 3.0 mm.
13. A method according to claim 1, further comprising the step of
providing a two phase liquid system having an upper phase
comprising said inert organic liquid phase and a lower phase
comprising said aqueous acidic solution, and wherein said steps of
passing said droplets and said spheres comprises the step of
passing said droplets through said two phase liquid system.
14. A method according to claim 1, wherein said inert organic
liquid phase is selected from the group consisting of kerosene,
hexane, toluene, mineral oil, vegetable oil, alcohol and mixtures
thereof.
15. A method according to claim 14, wherein said inert organic
phase further comprises an anionic surfactant.
16. A method according to claim 1, wherein said aqueous acidic
solution has a pH of between about 4 to about 5.
17. A method for preparing a catalyst system, comprising the steps
of:
providing a catalyst support comprising substantially spherical
particles of a substantially homogeneous mixture consisting of
silicon carbide and silica, wherein said particles have a surface
area of at least about 30 m.sup.2 /g an average pore diameter of at
least about 150 .ANG., and a particle size of at least about 0.1
mm;
supporting a catalytically active metal phase on said support
comprising at least one metal selected from the group consisting of
Group IVb metals, Group VIII metals, and mixtures thereof; and
calcining said catalyst support and supported catalytically active
phase at a temperature of between about 350.degree. C. to about
600.degree. C. so as to provide said catalyst system.
18. A method according to claim 17, wherein said supporting step
comprises supporting a first metal selected from Group IVb and a
second metal selected from Group VIII.
19. A method according to claim 17, wherein said first metal ius
selected from the group consisting of zirconium, titanium, hafnium
and mixtures thereof, and wherein said second metal is selected
from the group consisting of cobalt, iron, nickel, ruthenium, and
mixtures thereof.
20. A method according to claim 17, wherein said supporting step
comprises impregnating said support with at least one aqueous
solution of said at least one metal.
21. A method according to claim 20, wherein said at least one
aqueous solution of said at least one metal comprises a solution in
water of a water soluble salt of said at least one metal.
22. A method according to claim 21, wherein said water soluble salt
is selected from the group consisting of nitrates, oxalates,
sulfates, acetates, acetylacetanates, and mixtures thereof.
Description
BACKGROUND OF THE INVENTION
The invention relates to a hydrogenation catalyst. Specifically,
the invention relates to a catalyst having improved attrition
resistance and heat dissipation properties which is particularly
useful in the hydrogenation of a carbon monoxide feedstock so as to
obtain C.sub.2 + hydrocarbon products.
Numerous patents contain disclosures of processes for hydrogenation
reactions wherein carbon monoxide is upgraded to desirable
hydrocarbon products. One method of performing this hydrogenation
is to induce a Fischer Tropsch reaction, wherein carbon monoxide is
converted in an exothermic reaction to the desired end product.
Numerous types of reactors can be used for carrying out the
hydrogenation reaction. One type is known as an ebulliating bed
reactor. An ebulliating bed reactor is characterized by a vessel
containing a bed of the catalyst through which the feedstock is
passed, typically from the bottom toward the top of the reactor.
This results in a bed of the catalyst suspended in the medium and
subjected to continuous collisions. The catalyst itself remains
inside the reactor.
One problem encountered in the art with ebulliating reactors is the
attrition rate of the catalyst contained in the reactor. That is,
the catalyst tends to break down to smaller particles or fines
after any significant amount of use.
It is therefore a primary object of the present invention to
provide a catalyst system wherein the catalyst particles are
resistant to attrition.
It is a further object of the present invention to provide a
catalyst having good heat dissipation properties so as to assist in
dissipating heat generated by the exothermic hydrogenation
reaction.
It is a still further object of the present invention to provide a
catalyst system which has excellent activity and selectivity toward
desirable hydrogenation reactions for converting a carbon monoxide
feedstock to C.sub.2 + hydrocarbons.
It is another object of the present invention to provide a process
for preparing a catalyst system according to the invention.
It is still another object of the present invention to provide a
process for hydrogenation of carbon monoxide to C.sub.2 +
hydrocarbons using the catalyst of the present invention.
Other objects and advantages of the invention will appear
hereinbelow.
SUMMARY OF THE INVENTION
In accordance with the invention, the foregoing objects and
advantages are readily attained.
In accordance with the invention, a catalyst support is provided
which comprises substantially spherical particles of a
substantially homogeneous mixture of at least two compounds
selected from the group consisting of refractory inorganic oxides,
refractory inorganic carbides, refractory inorganic nitrides and
mixtures thereof, wherein said particles have a surface area of at
least about 30 m.sup.2 /g, an average pore diameter of at least
about 150 .ANG., and a particle size of at least about 0.1 mm.
In further accordance with the invention, a catalyst system for
hydrogenation of carbon monoxide feedstock is provided which
comprises a catalyst support comprising substantially spherical
particles of a substantially homogeneous mixture of at least two
compounds selected from the group consisting of refractory
inorganic oxides, refractory inorganic carbides, refractory
inorganic nitrides and mixtures thereof, wherein said particles
have a surface area of at least about 30 m.sup.2 /g, an average
pore diameter of at least about 150 .ANG., and a particle size of
at least about 0.1 mm, and a catalytically active metal phase
supported on said support and comprising at least one metal
selected from the group consisting of Group IVb metals, Group VIII
metals, and mixtures thereof.
The catalytically active phase may preferably comprise a first
metal selected from Group IVb, preferably zirconium, and a second
metal selected from Group VIII, preferably cobalt.
In further accordance with the present invention, a method for
preparing the catalyst support of the present invention is provided
which comprises the steps of forming a suspension comprising
particles of at least two compounds selected from the group
consisting of refractory inorganic oxides, refractory inorganic
carbides, refractory inorganic nitrides, and mixtures thereof in a
basic aqueous solution, adding a pore size controlling agent to the
suspension, forming droplets of the suspension, passing the
droplets through an inert organic liquid phase so as to form the
droplets into spheres, passing the spheres through an aqueous
acidic solution so as to provide at least partially solidified
spheres of said catalyst support.
In further accordance with the invention a method is provided for
production C.sub.2 + hydrocarbons by hydrogenation of carbon
monoxide, which method comprises the steps of providing a catalyst
system comprising a catalyst support comprising substantially
spherical particles of a substantially homogeneous mixture of at
least two compounds selected from the group consisting of
refractory inorganic oxides, refractory inorganic carbides,
refractory inorganic nitrides and mixtures thereof, wherein said
particles have a surface area of at least about 30 m.sup.2 /g, an
average pore diameter of at least about 150 .ANG., and a particle
size of at least about 0.1 mm, and a catalytically active metal
phase supported on said support and comprising at least one metal
selected from the group consisting of Group IVb metals, Group VIII
metals, and mixtures thereof, reducing said catalyst system under a
hydrogen atmosphere, providing a CO feedstock, and contacting said
CO feedstock and said catalyst system in the presence of reaction
hydrogen under hydrogenation conditions so as to produce C.sup.2
+.
BRIEF DESCRIPTION OF THE DRAWINGS
A detailed description of the preferred embodiments of the
invention follows, with reference to the attached drawings
wherein:
FIG. 1 illustrates prior art particles having silicon carbide and
silica; and
FIG. 2 illustrates a particle comprising an aggregate of particles
of silicon carbide and silica in accordance with the invention.
DETAILED DESCRIPTION
The invention relates to a hydrogenation catalyst support and
system, methods for preparing the catalyst system and support in
accordance with the invention, and a method for hydrogenation of a
carbon monoxide feedstock so as to provide C.sup.2 + products using
the catalyst system according to the invention.
According to the invention, a catalyst support is provided which is
useful in a catalyst system for hydrogenation of carbon monoxide
feedstocks. The catalyst support according to the invention has
enhanced resistance to attrition when used in an ebulliating bed
reactor, and further has enhanced heat dissipation qualities which
is desirable in light of the exothermic nature of the hydrogenation
reaction to be carried out in accordance with the invention.
The catalyst support of the present invention is provided in the
form of substantially spherical particles of a substantially
homogeneous mixture of at least two compounds selected from the
group consisting of refractory inorganic oxides, refractory
inorganic carbides, refractory inorganic nitrides and mixtures
thereof. The particles preferably are made up of a mixture of a
refractory inorganic oxide and a refractory inorganic carbide, most
preferably a mixture of silica and silicon carbide.
In further accordance with the invention, the particles comprise a
substantially homogeneous aggregate mixture of the silica and
silicon carbide. Referring to FIG. 1, it is known in the art to
provide a substrate of one or the other of silica and silicon
carbon and to deposit a coating of the other over the substrate, as
is shown in FIG. 1 wherein the shaded portion is silicon carbide
and the non-shaded portion is silica. Referring to FIG. 2, an
aggregate of silica and silicon carbide according to the invention
is illustrated. As clearly shown, the particles according to the
present invention are significantly different from that of the
prior art. Further, the aggregate structure of the catalyst support
of the present invention has been found to provide enhanced
resistance to attrition in an ebulliating bed reactor and further
provides for excellent activity and selectivity of a catalyst
system using the catalyst support of the present invention.
According to the invention, the particles of catalyst support
preferably have a surface area of at least about 30 m.sup.2 /g,
most preferably at least 40 m.sup.2 /g. Further, the particles
preferably have an average pore diameter of at least about 150
.ANG., more preferably of between about 200 to about 500 .ANG..
Further, the catalyst support according to the present invention
preferably has a pore diameter distribution such that at least
about 60% of the individual pore diameters of the particles are
greater than about 150 .ANG.. Most preferably, at least about 80%
of the individual pore diameters are greater than about 150
.ANG..
The catalyst support of the present invention is further
characterized by a particle size of at least about 0.1 mm,
preferably between about 0.1 to about 3.0 mm, and most preferably
between about 0.1 to about 1.0 mm.
In further accordance with the invention, the catalyst support is
preferably provided having silicon carbide present in an amount of
between about 10% to about 50% by weight of the catalyst support.
In increasing order of preference, the silicon carbide may be
present in the catalyst support particles in an amount of between
about 10-35, 15-30, and 15-26% by weight of the catalyst
support.
The catalyst support of the present invention is further
characterized by a pore volume of between about 0.2 cc/g to about
1.2 cc/g, more preferably between about 0.25 to about 0.60
cc/g.
In accordance with the invention, the for&going catalyst
support having the aforementioned physical characteristics has been
found not only to have excellent activity and selectivity in
hydrogenation reactions, but further has enhanced resistance to
attrition and improved heat dissipation properties.
In further accordance with the invention, the aforedescribed
catalyst support may be loaded, impregnated, or otherwise provided
with a catalytically active metal phase so as to provide the
catalyst system according to the invention. The hydrogenation
catalyst system of the present invention preferably has at least
one metal selected from Group IVb and Group VIII of the periodic
table of elements, and more preferably has at least two metals, one
selected from each of Group IVb and Group VIII. The Group IVb metal
is preferably selected from the group consisting of zirconium,
titanium, hafnium, and mixtures thereof, most preferably zirconium.
The Group VIII metal is preferably selected from the group
consisting of cobalt, iron, nickel, ruthenium, and mixtures
thereof, most preferably cobalt.
According to the invention, the Group IVb metal is preferably
present in an amount of between about 0.01% to about 25%,
preferably 0.01 to about 5% by weight, with respect to the catalyst
system. The Group VIII metal is preferably provided in an amount of
between about 1% to about 50%, preferably 6% to 25% by weight with
respect to the catalyst system. Further, the Group IVb and Group
VIII metals are preferably provided in a weight ratio of Group IVb
metal to Group VIII metal of between about 25:1 to about
1:8000.
Of course, the catalyst support according to the present invention
may be provided with numerous combinations of catalytically active
metals, particularly dependent upon the process for which the
catalyst system is to be used, the feedstock to be treated and the
desired end products. Further, although the present embodiment is
disclosed in terms of zirconium and cobalt supported on the
catalyst support, it should be appreciated that combinations of
more than two metals could of course be used if desired.
The combination of zirconium and cobalt as set forth above and in
the proportions as set forth above has been found according to the
invention to provide excellent activity and selectivity in the
hydrogenation of carbon monoxide feedstocks so as to provide
C.sup.2 + products.
According to the invention a method is also provided for preparing
the catalyst support and catalyst system of the present invention.
In accordance with the method of the present invention, the
aforedescribed catalyst support and system are provided having the
desired spherical particles of substantially homogeneous mixture of
silica and silicon carbide. The present method is instrumental in
providing the desired homogeneous mixture or aggregate of silica
and silicon carbide as illustrated in FIG. 2, rather than the
substrate with deposited component structure as illustrated in FIG.
1 which is obtained in accordance with the prior art.
According to the invention, the catalyst support of the present
invention may be provided by forming a suspension of particles of
the desired compound selected from the group consisting of
refractory inorganic oxides, refractory inorganic carbides,
refractory inorganic nitrides, and mixtures thereof in a basic
aqueous solution. In accordance with the invention, a pore size
controlling agent is preferably then added to the suspension so as
to induce the formation of the appropriate pore size in the
suspension. Next, droplets of the suspension are formed and passed
through an inert organic liquid phase which may preferably include
an anionic surfactant which acts to form the droplets of suspension
into spheres. The spheres of suspension are then passed in
accordance with the method of the present invention through an
aqueous acidic solution which serves to gel or at least partially
solidify these spheres so as to provide spherical particles of the
desired substantially homogeneous mixture or aggregate of the
silica and silicon carbide compounds.
In accordance with the invention, the suspension of support
compounds may be formed by providing a silica suspension or aquasol
such as Ludox AS40 which is provided by DuPont, preferably at a pH
of between about 9 to about 10. Particles of silicon carbide may
then be added to the silica suspension. The particles of compounds
to be provided in the suspension preferably have a particle size of
less than or equal to about 150 microns, preferably less than or
equal to about 50 microns.
Numerous additives may be utilized, if desired, to provide the
desired basic pH of the solution in which the suspension is formed.
The actual agent used to provide the pH forms no part of the
present invention.
The viscosity of the suspension may be adjusted in accordance with
the present invention so as to maintain the particulate compounds
in suspension during the catalyst forming method. In accordance
with the present invention, the viscosity controlling agent may be
added to the suspension so as to provide a viscosity of at least
about 50 cp at 25.degree. C., thereby maintaining the silica and
silicon carbide particles in suspension while the support is being
formed. Numerous viscosity controlling agents may be used in
accordance with conventional techniques. An example of a suitable
viscosity controlling agent is ethylene oxide polymer such as
Polyox WSR-205, supplied by Union Carbide.
In accordance with the invention, a pore forming agent is then
added to the suspension so as to provide the desired pores and pore
size in the suspension which result in the catalyst support having
the desired pore size characteristics as discussed above. Suitable
pore inducing or size controlling agents include
hexamethylenetetramine, urea, water soluble starch, and mixtures
thereof. The preferred pore size controlling agent is
hexamethylenetetramine.
The slurry of suspension and pore size controlling agent is then
preferably formed into droplets in accordance with the invention,
which droplets preferably have a size of between about 0.1 mm to
about 3.0 mm.
The desired droplets of suspension may be formed in accordance with
the invention using any known technique or equipment, such as, for
example a spinning disk atomizer or the like. Of course, numerous
methods and apparatus are known in the art for providing droplets
of a liquid phase, and the exact method or apparatus used forms no
part of the present invention.
In further accordance with the method for preparing the catalyst
support of the present invention, the formed droplets of desired
size are then passed sequentially first through an inert organic
liquid phase and then through an aqueous acidic solution. The
sequential passing of droplets through the aforementioned phases
serves to provide the droplets of suspension with the desired
spherical shape, and then to gel or at least partially solidify the
spherical droplets for final treatment steps such as calcining and
the like so as to provide the desired spherical particles of
substantially homogeneous mixture of silica and silicon carbide in
accordance with the invention.
The inert organic liquid phase may suitably be kerosene, hexane,
toluene, mineral oil, vegetable oil, alcohol, and mixtures thereof,
and may in accordance with the invention further include an anionic
surfactant to enhance the sphere forming nature of the inert
organic phase.
The aqueous acidic solution which induces the gelling of spheres of
the catalyst support in accordance with the invention preferably
has a pH of between about 4 to about 5. Any of numerous additives
may be provided in the aqueous solution so as to reduce the pH to
the desired level. As the droplets pass from the first solution in
spherical form, the second solution or phase stabilizes the spheres
as the gelification process is initiated.
In accordance with the invention, the first inert organic phase and
the second aqueous acidic solution phase may be provided in a
vessel having the first phase as an upper phase and the second
phase as a lower phase whereby droplets formed from the suspension
may be passed sequentially through the first phase and then the
second phase by allowing the droplets to sink through the vessel.
Of course, separate vessels may be provided for containing each of
the first or second phase and numerous other configurations may be
provided for passing the droplets sequentially through the first
and second phases so as to provide the at least partially
solidified spheres of substantially homogeneous mixture or
aggregate of silica and silicon carbide as desired.
In further accordance with the invention, the spheres obtained from
the aqueous acidic solution are then preferably dried, calcined,
and hydrothermally treated so as to provide the desired average
pore diameter and pore diameter distribution which, in accordance
with the invention, serve to provide the catalyst support with the
desired physical characteristics which have been found in
accordance with the invention to be particularly suitable for
hydrogenation of carbon monoxide.
According to the invention, the at least partially solidified
spheres obtained from the aqueous acidic solution are preferably
first dried in a conventional drying step so as to provide dry
spherical particles of the catalyst support.
The dry spherical particles are then preferably calcined at a
temperature of between about 350.degree. to about 600.degree. C.
The calcination is preferably carried out for a period of time
sufficient to remove all traces of solvents and additives and
thereby provide the desired solid spheres of silica and silicon
carbide in a substantially homogeneous mixture or aggregate in
accordance with the invention.
The calcined spherical particles may then be hydrothermally treated
at an elevated temperature which serves to collapse the smallest
pores of the particles so as to increase the average pore diameter
to at least about 150 .ANG., and preferably to between about 200 to
about 500 .ANG..
After hydrothermal treatment, the catalyst support is then
preferably calcined again at a temperature of between about
350.degree. to about 600.degree. C. so as to provide the desired
catalyst support having a surface area of at least about 30 m.sup.2
/g, a particle size of at least about 0.1 mm, and a pore volume of
between about 0.2 cc/g to about 1.2 cc/g.
The hydrothermal treatment and calcining steps are preferably
carried out so as to provide the catalyst support with a pore size
distribution wherein at least about 60%, and preferably at least
about 80% of individual pore diameters are greater than about 150
.ANG..
The aforementioned hydrothermal treatment and calcining steps are
carried out in accordance with known techniques which form no part
of the present invention.
In further accordance with the invention, the catalyst support
provided in accordance with the above-identified method may then be
provided with a catalytically active metal phase so as to provide a
catalyst system, preferably for use in hydrogenation of a carbon
monoxide feedstock. The catalyst support may be incorporated into a
catalyst system according to the invention by supporting a
catalytically active metal phase having at least one metal selected
from Group IVb and Group VIII of the periodic table of elements.
The catalytically active metal phase, as set forth above,
preferably includes at least two metals from the above-mentioned
groups, most preferably one Group IVb metal and one Group VIII
metal. The metals may be supported on the catalyst support through
any conventional procedure or technique such as sequential or
simultaneous impregnation, ion exchange, or any other suitable
procedure.
In accordance with the invention, the metal may be provided on the
support through impregnation of aqueous solutions containing the
desired metal. Suitable aqueous solutions may be formed by mixing a
water soluble salt of the desired metal in water. Suitable salts
include nitrates, oxalates, sulphates, acetates, acetylacetanates,
and mixtures thereof.
The catalyst support provided in accordance with the method of the
present invention has been found, in accordance with the present
invention, to be particularly well suited to hydrogenation of
carbon monoxide into desirable and more valuable C.sub.2 +
hydrocarbon products. In accordance with the present invention, the
process for treating carbon monoxide with the catalyst system of
the present invention comprises the steps of providing a catalyst
system including the catalyst support according to the invention
and a catalytically active metal phase supported on the support,
preferably in a suitable reactor such as an ebulliating bed
reactor. The catalyst system is preferably reduced under a hydrogen
atmosphere in accordance with the invention so as to provide the
catalyst system in the appropriate state for hydrogenation. In
accordance with the invention, a carbon monoxide feedstock is
provided and preferably mixed with reaction hydrogen to form a
reaction feedstock which is contacted with the reduced catalyst
system whereby the carbon monoxide feedstock is hydrogenated so as
to provide desirable C.sub.2 + hydrocarbon products.
The reaction feedstock and catalyst system are of course contacted
under hydrogenation conditions which are suitable and effective for
carrying out the hydrogenation reaction. The hydrogenation
conditions are preferably standard Fischer Tropsch conditions
suitable to produce C.sub.2 + hydrocarbons. Typical hydrogenation
conditions include, for example, a temperature of about 220.degree.
C., pressure of about 230 psig, GSHV of about 500 H.sup.-1, and a
ratio of hydrogen to carbon monoxide feedstock of about 2, although
of course the conditions vary depending upon the feedstock and the
desired reaction products.
In accordance with the invention, the catalyst support exhibits an
excellent resistance to attrition when used in an ebulliating bed
reactor. When arranged in such a reactor, for example, the catalyst
system of the present invention exhibits a bed strength of 20
kg/cm.sup.2 and produces only 0.1% of fine particles having a
particle size less than 250 microns. This represents a substantial
improvement over conventional catalyst systems for use in
ebulliating bed reactors. Furthermore, the refractory nature of the
silicon compounds of the catalyst support of the present invention
serve to provide improved heat dissipation characteristics which
are useful in the exothermic conditions of the hydrogenation
treatment for which the catalyst system is used.
The following examples illustrate the features of the catalyst
support, catalyst system, method for preparation and method for use
of the catalyst support and system for hydrogenation of carbon
monoxide in accordance with the invention.
EXAMPLE 1
This example illustrates the preparation of a catalyst support in
accordance with the method of the present invention. Four slurries
were prepared by mixing 1092 ml. of a silica aquasol (Ludox AS40 at
pH 10, DuPont) with four different amounts of silicon carbide
having a particle size of less than or equal to 30 microns.
Ethylene oxide polymer (Polyox WSR-205, Union Carbide) was added to
the suspension at a concentration of 300 ppm so as to adjust the
viscosity of the suspension or slurry to a value exceeding 50 cp at
25.degree. C. A pore forming agent, hexamethylenetetramine, was
then added to the suspension. The suspension was then delivered by
spinning disk atomizer to a vessel containing a two phase liquid
having an upper phase composed of kerosene and an anionic
surfactant and a lower phase containing an aqueous buffer with a pH
which was maintained between about 4 to about 5. As the formed
droplets sink through the organic phase, the droplets attain a
spherical form which is stabilized by the presence of the anionic
surfactant. When the spherical droplets of slurry or suspension
enter the acidic phase, the gelification process initiates so as to
stabilize and at least partially solidify the spherically formed
droplets of suspension. The spheres were then recovered and dried
overnight at 40.degree.. The dried spheres were then calcined at
500.degree. C. so as to remove all traces of solvent and additive.
The spheres were then hydrothermally treated at 180.degree. C. so
as to increase the average pore diameter of the spheres, which were
then calcined again at 500.degree. C. The resulting spherical
particles had an average particle size of about 0.65 mm.
Four catalyst supports were prepared from the slurries in
accordance with the above procedure, each having a different weight
percentage of silicon carbide. The characteristics of each support
are set forth below in Table I.
TABLE I ______________________________________ PORE SURFACE PORE
DIA- Pore Diameter SUP- SiC AREA VOLUME METER Distribution (%) PORT
WT % m.sup.2 /g cm.sup.3 /g .ANG. <150 .ANG. >150 .ANG.
______________________________________ 1 0 48 0.42 350 6.58 93.42 2
15 51 0.41 322 15.12 84.88 3 26 40 0.42 420 4.36 95.64 4 35 40 0.41
410 6.32 93.68 ______________________________________
As set forth in Table I, the method for providing the catalyst
support in accordance with the invention results in the catalyst
support having physical characteristics such as surface area, pore
volume, average pore diameter and pore diameter distribution all
within the desired ranges as set forth in the invention.
EXAMPLE 2
This example illustrates the preparation of a catalyst system
wherein the catalyst support of Example 1 is impregnated with
zirconium and cobalt. The four samples of catalyst support prepared
in Example 1 were co-impregnated with the desired active metals
using a pore saturation method with solutions containing
ZrONO.sub.3.H.sub.2 O and Co(NO.sub.3).sub.2.H.sub.2 O. The
catalysts were prepared so as to contain 8% by weight of cobalt and
1% by weight of zirconium. The impregnated supports were dried at
260.degree. C. and calcined at 360.degree. C. to oxidize the metal
phase. Table II set forth below contains the physical
characteristics of each catalyst system prepared from supports 1-4
of Example 1.
TABLE II ______________________________________ PORE SURFACE PORE
DIA- Pore Diameter CATA- SUP- AREA VOLUME METER Distribution (%)
LYST PORT m.sup.2 /g cm.sup.3 /g .ANG. <150 .ANG. >150 .ANG.
______________________________________ A 1 46 0.35 304 14.88 85.12
B 2 50 0.34 272 7.31 92.69 C 3 40 0.36 360 13.58 86.42 D 4 41 0.34
331 7.59 92.41 ______________________________________
EXAMPLE 3
This example illustrates the effect of the composition of the
catalyst support on the activity of the catalyst system based
thereon. Catalyst systems A-D as set forth in Table II above were
provided having an average particle size of about 0.8 mm and used
to hydrogenate a carbon monoxide feedstock at a temperature of
220.degree. C., a pressure of 230 psig, a ratio of hydrogen to
carbon monoxide of 2, and a GHSV of 500 H.sup.-1. The results of
each reaction, carried out in a fixed bed reactor, are set forth
below in Table III.
TABLE III ______________________________________ CATALYST A B C D
______________________________________ % SiC 0 15 26 35 CONVERSION
81 81 80 82 PRODUCTS: (% mol) CH.sub.4 10 11 8 8 C.sub.2 + 85 86 89
90 CO.sub.2 5 3 3 2 ______________________________________
As shown in Table III, the conversion of carbon monoxide remains
substantially the same regardless of the concentration of silicon
carbide in the support. However, the selectivity of the catalyst
toward C.sub.2 + hydrocarbons increased with the increase in
concentration of silicon carbide.
EXAMPLE 4
This example illustrates the effect of the particle size of the
catalyst system on the activity and selectivity of the catalyst
when used in hydrogenation reactions. Three catalyst systems (E, F,
G), were prepared containing 26% by weight silicon carbide in
accordance with the procedure of Example 1. The catalyst supports
were prepared having particle sizes ranging between 0.65 mm to 2.5
mm. Each support was impregnated as in Example 2 with 8% weight
cobalt and 1% weight zirconium. Each catalyst was used in a
hydrogenation procedure of a carbon monoxide feedstock at a
temperature of 223.degree. C., a pressure of 300 psig, a hydrogen
to carbon monoxide ratio of 2, GHSV of 500 H.sup.31 1, and a
paraffin flow of 60 cc/min. The reactions were carried out in an
ebulliating bed reactor, and the results are set forth below in
Table IV.
TABLE IV ______________________________________ CATALYST E F G
______________________________________ SIZE (mm) 2.5 1.8 0.65
CONVERSION 37 57 56 PRODUCTS: (% mol) CH.sub.4 23 22 9 CH.sub.2 +
76 77 89 CO.sub.2 1 1 2 ______________________________________
As shown, the particle size of 0.65 yielded the highest selectivity
to C.sub.2 + hydrocarbon products as desired. Further, conversion
increased as the particle size decreased from 2.5 mm.
EXAMPLE 5
This example illustrates the effect of the surface area of the
catalyst of the present invention on its activity when used in
hydrogenation reactions. Two catalyst (H, I), were prepared as
described in Example 2 having 12% weight cobalt and 1.5% weight
zirconium. Catalyst H was calcined as described in Example 2 while
Catalyst I was calcined at a temperature of 850.degree. C. so as to
obtain a smaller surface area. A reaction was then carried out in a
fixed bed reactor under the reaction conditions set forth in
Example 3, and the results are set forth below in Table V.
TABLE V ______________________________________ SURFACE CONVER-
CATA- AREA SION PRODUCTS (% mol) LYST m.sup.2 /g % CH.sub.4 C.sub.2
+ CO.sub.2 ______________________________________ H 40 80 8 89 3 I
21 42 16 80 4 ______________________________________
As shown, the decrease in surface area adversely effects both
activity and selectivity of the catalyst. The smaller surface area
causes a shift in reaction products towards undesirable CO.sub.2
and C.sub.4 and away from the desirable C.sub.2 + products.
EXAMPLE 6
This example illustrates the effect of the pore diameter of the
catalyst system of the present invention on the conversion of CO
and hydrogenation reactions. Three catalysts (H as in Example 5
above, P and J) were prepared as described in Example 2 and loaded
with 12% weight Cobalt and 1.5% weight zirconium. Catalysts P and J
were not subjected to varying hydrothermal treatments so as to
provide smaller pore diameter as set forth below in Table VI. Each
catalyst system was then used in a hydrogenation reaction procedure
as described in Example 3. The results of the reactions are also
set forth below in Table VI.
TABLE VI ______________________________________ PORE DIAMETER
PRODUCTS (% mol) CATALYST .ANG. CH.sub.4 C.sub.2 + CO.sub.2
______________________________________ H 270 9 86 5 P 150 19 77 4 J
11 58 2 40 ______________________________________
As shown, the decrease in pore diameter out of the preferred range
in accordance with the present invention caused a shift of the
product of the hydrogenation reaction away from the desirable
C.sub.2 + products and toward undesirable CH.sub.4 and CO.sub.2
products.
EXAMPLE 7
This example illustrates the effect of the cobalt and zirconium
concentrations of the catalyst system on the conversion of carbon
monoxide. Six catalyst systems were prepared as described in
Example 2, each with differing concentrations of cobalt and/or
zirconium as set forth below in Table VII. The catalysts used in
this example were Catalyst H as discussed in Example 5 above, and
Catalysts K, L, M, N and O each having the concentration of cobalt
and zirconium as listed below in Table VII. Each catalyst was used
in a carbon monoxide hydrogenation reaction as described in Example
3, with the results of the reaction also being set forth below in
Table VII.
TABLE VII ______________________________________ CATALYST H K L M N
O ______________________________________ Co % wt 12 8 20 25 16 6 Zr
% wt 1.5 1.0 10 3 5 0.001 Conversion % 96 85 95 98 74 58 Products:
% mol CH.sub.4 9 7 12 13 9 8 C.sub.2 + 86 92 82 79 90 90 CO.sub.2 5
1 6 8 1 2 C.sub.4 -/C.sub.4 0.25 -- 0.19 -- -- 0.86
______________________________________
In accordance with the invention, zirconium in the catalyst serves
to improve the selectivity of the catalyst toward the production of
paraffins.
EXAMPLE 8
This example illustrates the resistance of a catalyst system in
accordance with the invention to attrition when used in an
ebulliating bed reactor. A support was prepared as described above
in Example 1 and provided with a particle size of 0.65 mm. The
support was placed in a column having 100 cm in height and an
internal diameter of 4 cm. The column was filled with 100 cm.sup.3
of the support and an air/water mixture was injected into the
bottom of the column at room temperature for 30 days. The air was
fed at 1300 H.sup.-1 with a speed of 191 cm/min., while the water
was fed at 240 H.sup.-1 at a speed of 32 cm/min. After 30 days of
operation, the fine production measured in the terms of particulate
having a size smaller than 250 microns was less than 7% weight of
the catalyst support, which demonstrates an excellent resistance to
attrition.
Thus provided is an improved catalyst support and catalyst system
which exhibits enhanced resistance to attrition, improved heat
dissipation qualities, and an excellent activity and selectivity in
the hydrogenation of carbon monoxide so as to provide C.sub.2 +
hydrocarbon products. Further, a method is provided in accordance
with the invention for preparing the catalyst support and system
having the desired physical characteristics which have been found
in accordance with the invention to be instrumental in providing
the above-identified advantages of the catalyst in accordance with
the present invention. Also provided is a method for hydrogenating
a carbon monoxide feedstock using the catalyst system of the
present invention so as to convert the carbon monoxide feedstock
into desirable and more valuable C.sub.2 + hydrocarbon
products.
It is to be understood that the invention is not limited to the
illustrations described and shown herein, which are deemed to be
merely illustrative of the best modes of carrying out the
invention, and which are susceptible of modification of form, size,
arrangement of parts and details of operation. The invention rather
is intended to encompass all such modifications which are within
its spirit and scope as defined by the claims.
* * * * *